1. Field of the Invention
The present disclosure herein relates to a semiconductor memory device, and more particularly, to a passive wireless memory device.
2. Description of the Related Art
Radio Frequency Identification (RFID) technology is a field of automation data collection systems, which includes RFID tags and RFID readers. RFID tags transmit data to RFID readers in response to signals from the RFID readers.
RFID tags are attached to identification subjects such as automobiles, goods, and livestock to store information to identify the subjects. RFID readers receive information stored in the RFID tags in a contactless manner via wireless communication. That is, since RFID technology does not require direct contact or scanning in the visible band, the RFID technology is esteemed as an alternative technology to bar codes and has a wide applicable range, or varied applicable uses.
Particularly, the application potential of the RFID technologies is steadily increasing because encoding of information and renewal of data are possible in the RFID technology unlike a typical bar code technology and a larger amount of information may be more quickly delivered than in the bar code technology.
In general, the RFID technologies may be divided into technologies related to RFID tags and technologies related to RFID readers for reading the RFID tags. More specifically, the RFID technologies may be divided into detailed technical categories such as types of RFID tags, configuration of middleware, configuration for mobilization, and security-related configuration.
RFID tags store sensing information and identification codes of objects, and transmit stored information according to requests from RFID readers or other devices. RFID tags utilize aspects of various technologies including antenna and wireless signal processing, chip technologies, thin-film batteries, packaging technologies, and chip-downsizing technologies. RFID tags are divided into active RFID tags and passive RFID tags according to whether the RFID tags include their own power sources.
Active RFID tags have a relatively long communication distance and high transmission rate and enable transmission of large-capacity data. However, active RFID tags require periodic management, and have larger volumes and difficulties in installation due to internal power sources.
On the other hand, passive RFID tags are supplied with operating power from radio waves of RFID readers. Passive RFID tags have semi-permanent durability, and have more advantages than bar codes. Accordingly, passive RFID tags are used in logistic management systems, security systems, and logistic tracking systems. On the other hand, since passive RFID tags use power induced by approach of RFID readers as a power source, the passive RFID tags do not require a separate power source. However, the passive RFID tags have relatively short communication distances, and have difficulties in using large-capacity memories due to limitation of power management, resulting in restriction of the amount of transmission data.
Therefore, using the advantages of the active RFID tags provides large-capacity data and reduces the burden due to management or installation, and using the advantages of the passive RFID tags provides ease of management or installation and provides large-capacity data. Accordingly, many studies are being conducted to utilize RFIDs for applications required to provide multimedia or mass information